The present invention relates to a valve for regulating the through-flow of a fluid from an inlet to an outlet, especially for regulating a gas flow from a place with a higher pressure than the ambient pressure, the valve being arranged to be opened by an operating means which is mechanically coupled to a means sensing the pressure at said place. Further, the invention relates to a double-acting valve device including such a valve, especially a breathing valve for divers wherein the valve constitutes an exhalation valve.
A topical field of application for such a regulating valve is in breathing systems for divers. Such systems for the supply of breathing gas are generally based on regulated supply from reservoirs of high-pressure gas. Usually, the through-flow of gas is controlled in such a manner that it corresponds to the demand, i.e. the system is a so-called demand system.
From Norwegian Patent Specification No. 151,447 there is known a gas regulator valve which is designed as an inhalation valve, which valve affords a precise control with a minimum of force consumption in the opening of the valve. The known valve is regulated by axial displacement of a piston, the pressure difference on the two end faces of the piston being equalized by means of a control valve which opens for a pressure equalizing channel through the piston. The piston is mounted in a cylindrical guide of which one end has a contriction acting as a sealing surface/seat for the piston, and of which the other end is closed. The valve is in closed position when the piston with one end face rests against said sealing surface/seat and the pressure equalizing channel is closed. The gas flow through the valve is via channels through the wall of the cylindrical guide and further through the constriction in the guide.
The cylindrical piston guide, one end face of the piston and the closed end portion of the piston guide define a chamber which is of fundamental importance for the gas regulation, the chamber together with the pressure equalizing channel making it possible to obtain approximately the same gas pressure on both sides of the piston before this is moved to open position, so that the gas flow can be regulated with a small force. The force which is necessary to move the piston with the pressure equalizing channel closed, typically may be of the order of 20 times larger than with the channel open.
The known valve according to said Norwegian patent specification generally can be used for maintaining a stable secondary pressure. This is of topical interest for example in a common sports diver valve wherein one wants the diver to be supplied with gas of the same pressure as the pressure of the surrounding water. However, this valve structure cannot be used for regulating exhaled gas. The valve is then wanted to "draw out" gas as soon as the pressure in the valve housing exceeds the surrounding pressure. In this situation, the primary pressure is synonymous with the pressure in the valve housing. The valve must try to keep this pressure constant. Such a valve may be called a "back-pressure" valve. A traditional regulating valve has for its task to provide for supplying gas when this is required in order to maintain a stable pressure in the valve housing (=the ambient pressure). The back-pressure valve shall, on its part, provide for letting out gas when this is required for maintaining the pressure.